BOLT CARRIER FOR SEMI-AUTOMATIC and AUTOMATIC FIREARM

ABSTRACT

A firearm magazine and a corresponding bolt carrier assembly are provided herein. The firearm magazine includes a magazine body, with the magazine body having a width to accommodate a double stack of cartridges in a zigzag pattern. The firearm magazine also includes a spring coupled to a follower within the magazine body. The magazine body also includes two feed lips coupled to the magazine body, where the two feed lips together hold a single cartridge in place in a center of the magazine body to allow a bolt carrier to push the single cartridge out of the firearm magazine and into a chamber of a firearm. The bolt carrier includes feed lip channels configured to accommodate the feed lips therein. A cocking surface is located between the feed lip channels and has a width of less than 0.400 inches.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.16/029,317, filed on Jul. 6, 2018, which is incorporated herein byreference.

BACKGROUND Field

Embodiments of the present disclosure generally relate to firearmmagazines and corresponding firearm parts. More specifically, thedisclosure relates to an improved high capacity magazine design thatallows for the feeding of ammunition without the use of feed rampsand/or allows an existing magazine to be used for larger cartridges thanthe magazine's original design.

Description of the Related Art

Magazines for automatic and semi-automatic firearms are often of thehigh capacity design to provide the firearm with a reasonable amount ofammunition. Magazines can be comprised of metal, various polymers, orany other suitable material, including a combination of materials.Magazines may be made as one piece of folded material or as multiplesections attached together.

To maximize the use of the space inside the magazine, and to keep themagazine as small as possible, the ammunition is often arranged in a“double stack” configuration to reach the high capacity desired. Doublestack refers to the two vertical columns of cartridges arranged next toeach other in a staggered zigzag pattern (see FIG. 1A) when the magazineis loaded. The magazines are also configured in a “double feed”configuration. That is, the double feed design has two feed lips—one oneach side of the magazine which holds the top cartridge in each stack inplace. Each feed lip of the double feed design retains one cartridge.FIG. 1A illustrates a magazine 100 utilizing a double stack/double feedconfiguration. The cartridges 114 are arranged inside the magazine body102 as illustrated. These two columns of cartridges 114 extend from thetop to the bottom of the magazine 100 when the magazine 100 is fullyloaded.

The magazine 100 has a coil type spring 104 on the inside of themagazine 100 that extends from the bottom of the magazine 100 to thetop. A floor plate 112 is at the bottom of the magazine 100. On top ofthe spring 104 is a plastic or metal piece called a follower 106 formedto guide the cartridges 114 into place as the cartridges 114 are loadedinto the magazine 100. As the magazine 100 is loaded, the spring 104compresses until the magazine 100 is fully loaded. The cartridges 114are contained inside the magazine 100 by feed lips 108 at the top of themagazine 100. There are two feed lips 108 on a double stack/double feedconfigured magazine, one on each side of the magazine. The feed lips 108are curved pieces of metal or plastic that are attached to and extendfrom the sides of the magazine 100. The feed lips 108 are curved at adesired angle to maintain the top-positioned cartridge 114 in positionin the magazine 100. As shown in FIG. 1A, each feed lip 108 retains onecartridge 114: the cartridge 114 that is on the side of the magazine 100that the respective feed lip 108 is on. In this example, the left feedlip 108 is retaining the topmost cartridge 114 in the magazine 100.After the topmost cartridge 114 is removed from the magazine 100 andchambered into the firearm, the next highest cartridge 114 at the top ofthe right side stack of cartridges 114 moves into the topmost positionin the magazine 100 and held in position by the right feed lip 108.

The cartridges 114 are held up against the underside of feed lips 108 bythe upward force exerted by the magazine spring 104. There is a space(e.g., a bolt channel 110) between the inside edges of the two feed lips108 to allow a bolt of the firearm to pass through as the bolt movesforward and pushes the cartridges 114 out of the magazine 100 and intothe chamber of the firearm.

FIG. 1B illustrates a magazine 150 having a single stack/single feedconfiguration. Cartridges 114 are arranged in a single vertical stackwithin the magazine body 102. Feed lips 108 both hold the topmostcartridge 114 at the top of the magazine 150, with the bolt channel 110between the feed lips 108. The follower 106, the spring 104, and thefloor plate 112 operate similarly to the double stack/double feedmagazine described above in FIG. 1A. A single stack/single feed magazineis generally thinner than a double stack/double feed magazine of similarlength and caliber, but the single stack/single feed magazine holdsfewer cartridges.

FIG. 2 illustrates a top view of double stack/double feed magazine 100.As shown, the cartridges 114 are arranged in a staggered zigzag patternwithin the magazine body 102. The bolt channel 110 is shown between thefeed lips 108. During operation, the cartridges 114 are removed or“stripped” from the magazine 100 by the bolt of the firearm as the boltcycles back and forth during firing. The bolt removes the top cartridge114 in magazine 100 each time a cartridge 114 is fired. A cartridge 114is removed from one side of the magazine 100 and then a cartridge 114 isremoved from the other side of the magazine 100, in an alternatingpattern, until the magazine 100 is empty. As shown in FIG. 2, the feedlip 108 on the left is holding the top cartridge 114 in place.

FIG. 3 illustrates an empty double stack/double feed magazine 100containing no cartridges 114. Spring 104 is extended from the bottom ofthe magazine 100 (near floor plate 112) to the top of the magazine 100,where the follower 106 is shown near the feed lips 108 and the boltchannel 110.

FIG. 4 illustrates top, side, and rear views of a double stack/doublefeed magazine 100, curved with stiffening grooves 116. As seen in theside view of the magazine 100, the magazine 100 is curved and includes anumber of stiffening grooves 116. The feed lips 108 are also visible inthe top, side, and rear views of the magazine 100. The bolt channel 110is shown in the rear and top view of the magazine 100.

FIG. 5 illustrates top, side, and rear views of a double stack/doublefeed magazine 100, straight with stiffening grooves 116. As seen in theside view of the magazine 100, the magazine 100 is straight from the topto the bottom, and includes a number of stiffening grooves 116. The feedlips 108 are also visible in the side and rear views of the magazine100. The bolt channel 110 is shown in the rear and top view of themagazine 100.

FIG. 6 illustrates top, side, and rear views of a double stack/doublefeed magazine 100, curved without stiffening grooves. As seen in theside view of the magazine 100, the magazine 100 is curved. The feed lips108 are also visible in the top, side, and rear views of the magazine100. The bolt channel 110 is shown in the rear and top view of themagazine 100.

FIG. 7 illustrates top, side, and rear views of a double stack/doublefeed magazine, straight without stiffening grooves. As seen in the sideview of the magazine 100, the magazine is straight. The feed lips 108are also visible in the side and rear views of the magazine 100. Thebolt channel 110 is shown in the rear and top view of the magazine 100.

Conventional double stack/double feed magazines have several benefits,such as maximizing the space available to contain as many cartridges aspossible while keeping the magazine as small as possible. However, thereare also drawbacks to the conventional double stack design. As mentionedabove, double stack configured magazines utilize a feed lip on each sideof the magazine to contain and align the cartridges in a horizontal tipforward position.

The chamber of a firearm is located in the center of the barrel. Adouble stack/double feed configured magazine presents the cartridges ina low offset position as the cartridges relate to the chamber of thefirearm, with each stack of cartridges off to a side of and just belowthe chamber, as illustrated in FIGS. 1A and 2. For the cartridges fromthe two columns in the magazine to enter the chamber correctly, thecartridges must be directed into the chamber from the cartridge's offsetpositions in the magazine.

FIG. 8 illustrates a front view of a barrel extension 200 with feedramps 202. The cartridges in a double stack/double feed magazine aredirected into the chamber of the firearm by feed ramps 202 locateddirectly in front of the top cartridge on each side of the magazine.These feed ramps 202 are angled channels or ramps machined into thebarrel extension 200 attached to the barrel of the firearm and are usedto guide the cartridges into the chamber 204 as the cartridges arepushed forward and out of the magazine by the bolt. As the bolt cycles,the top cartridge located under the feed lip of the magazine is pushedforward by the bolt of the firearm, and the cartridge moves in astraight horizontal fashion until the projectile in the cartridgecontacts the beveled feed ramp 202 on the barrel extension 200. As thecartridge continues to move forward the cartridge is deflected upwardand inward towards the center line of the firearm and into the chamber204 of the firearm.

When the cartridge is pushed forward by the bolt as the firearm cycles,the cartridge is moved with a great amount of force and velocity. Whenthe projectile in the cartridge engages the steel feed ramp 202 withthis force, the tip of the projectile can be dented or deformed whichdegrades the aerodynamic properties of the projectile thereby reducingaccuracy of the projectile.

Additionally, hunters often use soft point ammunition with exposed softlead tips that are required for hunting and that accelerate theexpansion of the projectile. These exposed lead tips can be severelydamaged by the feed ramps 202, degrading the accuracy of the huntingammunition and resulting in wounded or wasted animals.

Another drawback to the use of feed ramps 202 in barrel extensions 200of semi-automatic and automatic firearms to deflect and direct thecartridges into the chamber 204 of the firearm is that each feed ramp202 is located just below a bolt lug recess cut into the barrelextension 200. Bolt lug recesses 206 are illustrated in FIG. 8. Thebarrel extension 200 is a round metal collar screwed onto the back ofthe barrel that has teeth or “lugs” 212 that give the bolt of thefirearm something to lock into to contain the high pressures of thecartridge when the cartridge is fired. Between each barrel extension lug212 of the barrel extension 200 is a recess 206 or slot that allowspassage of the lugs on the bolt to pass through as the bolt enters thebarrel extension 200 and locks thereinto. In one or more embodiments,each of the lugs on the bolt corresponds to at least one of the bolt lugrecesses 206 of the barrel extension 200. In some embodiments, each ofthe lugs on the bolt corresponds to one of the bolt lug recesses 206 ofthe barrel extension 200.

The bolt lug recesses 206 have a square shape with sharp edges 208 onall three sides. As the cartridge is deflected into the chamber, theprojectile impacts the feed ramps 202 and passes through the bolt lugrecess 206. As the cartridge passes through, the projectile often comesinto contact with the sharp edges 208 which can further damage thejacket of the projectile and further degrade the projectile's accuracy.The damage to the projectile by the barrel extensions' sharp lug recessedges 208 becomes more severe as the caliber of the projectileincreases. Smaller caliber projectiles that are close to the width ofthe recess 206 may pass through with little or no damage, but largercaliber projectiles can receive major damage as the large projectileattempts to pass through the narrow recess 206. Feeding of largeprojectiles can even cause enough of a drag as the projectile's jacketdigs into the sharp edges of the recess 206 to slow down the bolt of thefirearm and cause the firearm to malfunction.

Military and law enforcement snipers as well as civilian competitionshooters often prefer semiautomatic rifles and use match ammunitionloaded with match grade projectiles that deliver excellent accuracy atextreme distances. Match grade projectiles are manufactured to exactingtolerances for consistency, including almost identical weights, jacketthickness concentricity, aerodynamic profiles, and perfectly formedtips. When these match grade projectiles engage the steel feed ramps 202and sharp edges 208 of the bolt lug recesses 206, the match gradeprojectiles are often deformed which is detrimental to the precisiondesign of the match grade projectiles and defeats the intended purposeof the match grade projectiles for improved long range accuracy.Degraded accuracy of match ammunition used by military and lawenforcement snipers could mean the difference between life and death fora hostage or bystanders.

The most common semiautomatic firearm in use today by the military, lawenforcement and civilian shooters is the AR15 (or AR10) style rifle. Oneof the reasons for the popularity of the AR15 style rifle is the modulartwo piece design of the AR15 style rifle which allows the upper andlower receivers to be exchanged with alternative upper or lowerreceivers. This modular design allows the owner of one lower receiver tohave multiple upper receivers, and therefore multiple calibers for onefirearm. The lower receiver contains the magazine well, which is therecess where the magazine is inserted into the firearm. The magazinewell is a fixed size and only accepts one size of magazine.

While the upper receiver of the firearm can be replaced easily to changefrom one caliber or cartridge to another, altering the magazine toaccept additional cartridges is not as easy. The double stack/doublefeed design magazines for AR15 type (or AR10) rifles have been slightlymodified successfully to accept several slightly larger cartridges, butthe double stack design magazine also has limitations to the size ofcartridges the double stack magazine can accept. The two major limitingfactors are feed lip adaptability and stack geometry.

As discussed above, feed lips 108 are metal flaps attached to thesidewall of the magazine 100 that are bent over the top of the magazine100 to contain the cartridges 114 inside the magazine 100 and to helpguide the cartridges 114 into the chamber 204. Feed lips 108 are curvedat an angle to retain the cartridge, for which the magazine wasdesigned, in the magazine. There is also a minimum amount of spacerequired between the feed lips 108 for the bolt of the firearm to passthrough the bolt channel 110 as the bolt pushes the cartridges 114 outof the magazine 100 and into the chamber 204 (see, e.g., FIGS. 1A, 2,and 8).

In one or more embodiments, a cartridge includes a case (not shown), aprojectile (not shown), an ignition source (not shown), and a propellant(not shown). In one or more embodiments, the case is fabricated from abrass containing material. The case is cylindrical in shape and at leastpartially defines a volume therein. The ignition source is disposed atthe first end of the case. The propellant is disposed in the volume. Theprojectile is at least partially inserted in the second end of the case.A diameter of the cartridge is a largest diameter of the case betweenthe first end and the second end.

As the cartridge case gets larger in diameter, the width of each feedlip 108 must also be increased to securely hold the larger case inplace. As the width of the feed lips 108 is increased, the width betweenthe two feed lips 108 is reduced. The width between the two feed lips108 determines the “bolt channel” 110, which is required for the firearmto operate, and thus limits the diameter of the cartridge case thedouble stack/double feed magazine 100 can adapt to.

FIG. 9 illustrates a sectioned side view of the barrel extension 200.Barrel extension lugs 212 are visible, and the bolt lug recesses 206 arenot visible but are illustrated by a dotted line. Chamber 204 is shownin barrel 210. Feed ramps 202 are also illustrated.

As the cartridge case becomes larger in diameter, the tip of theprojectile is located in a lower position in relation to the feed ramp202 when compared to a smaller diameter cartridge case because the feedlips 108 are in a fixed location and cannot be moved. For example, alower projectile position 220 for a double feed magazine is illustratedwith an arrow in FIG. 9. When the tip of the projectile is located inthis lower projectile position 220, the projectile may miss the leadingedge of the feed ramp 202 and stop moving forward when the projectilehits the flat inside surface of the barrel extension 200 or upperreceiver, thereby causing a feed jam and causing the firearm tomalfunction.

Stack geometry refers to the way the cartridges 114 position themselvesand move inside the magazine 100 when the magazine is loaded. Magazinesare originally designed and built for a specific cartridge diameter. Atraditional double stack type of magazine has a width to accommodate twovertical columns of selected cartridges side by side in a zigzag patternfrom top to bottom, as illustrated in FIG. 1A. With “good stackgeometry,” the entire stack of cartridges moves freely up and downinside the magazine with virtually no outward forces or resistance inthe magazine. As such, the cartridges “feed” correctly into the firearmand the magazine is reliable. FIG. 13B illustrates a double stackmagazine where the forces on the cartridges 114, such as force 510, aregenerally vertical within the magazine body 502. The vertical forces 510enable the cartridges 114 to move up and down inside the magazine body502 and feed correctly.

The width of the cartridge stack in a traditional double stack magazineis approximately 188% of the diameter of the cartridge case. In thisconfiguration, each cartridge in the stack, except for the top andbottom cartridges, is touching at least two other cartridges in thestack. Some of the cartridges may touch three or four other cartridgesin the stack.

As mentioned above, the magazine has a predetermined physical size towhich the magazine is limited to accommodate the magazine well of thefirearm. When attempting to modify the magazine to accept largerdiameter cases, the “stack geometry” inside the magazine changes. Theinternal dimensions of the magazine cannot be made larger or modifiedmuch because the double feed configuration requires a cartridge undereach feed lip 108 on each side of the magazine. As the cartridge casesget larger in diameter, the cartridge cases have larger spacestherebetween when the magazine is loaded, which creates an outward forceon the sides of the magazine. FIG. 12B illustrates forces 512 that cancreate an outward force on the sides of the magazine when the magazineis loaded with cartridges having a diameter larger than what themagazine was designed for, or when the width of the magazine is narrowerthan a conventional double stack magazine.

When this happens, the cartridges in the magazine do not move up anddown freely inside the magazine and can actually cause a bulge in theouter walls of the magazine. This can cause the cartridges to jamtogether inside the magazine, causing a feed jam and the firearm tomalfunction. This bulging of the magazines side walls also makes itdifficult to insert and release the magazine from the firearm. Doublestack/double feed types of magazines can therefore be modified to acceptcartridges larger than originally designed, but only minimally.

When attempting to narrow the width of the double stack of cartridgesthere is a width or range that alters the up and down forces of thedouble stack of cartridges and redirects the forces on the cartridges tothe outside walls of the magazine (see, e.g., FIG. 12B).

This “failure or wedge zone” where the cartridges exert forces to theoutside walls of the magazine is from approximately 150% to 180% of thediameter of the cartridge case. Previous attempts to adapt largercartridges to existing magazines have resulted in failure because theyhave attempted to adapt the cartridges to a stack width that falls inthis failure zone.

What is needed is an improved magazine design for semiautomatic andautomatic rifles, as well as a design that can be adapted for boltaction rifles.

SUMMARY

The present disclosure generally relates to firearm magazines forautomatic and semi-automatic firearms, and more particularly to a designthat allows for the advantages of a double stack magazine for highcapacity while utilizing a single feed style mechanism for positioningand guiding the cartridges into the chamber. An improved magazine designallows for the use of larger diameter cartridges other than what themagazine was originally designed for, allowing larger diametercartridges for use in smaller firearms. In military applications, largerdiameter cartridges may be more effective against armor used by opposingforces. Embodiments described herein allow an existing lower receiver toshoot larger diameter cartridges without requiring the purchase of a newweapon. An improved magazine design also utilizes a single feed design,allowing the internal width of the magazine to be adjusted to provide anefficient stack geometry without affecting the feeding of the cartridgesfrom the magazine.

In one or more embodiments, a firearm magazine includes a magazine body,with the magazine body having a width to accommodate a double stack ofcartridges in a zigzag pattern. The firearm magazine also includes aspring coupled to a follower within the magazine body. The firearmmagazine body also includes two feed lips coupled to the magazine body,where the two feed lips together hold a single cartridge in place in acenter position of the magazine body to allow a bolt to push the singlecartridge out of the firearm magazine and into a chamber of a firearm.

In some embodiments, a bolt carrier assembly is provided and includes abody having an elongated cylindrical shape with a first end opposite asecond end. The body has a central axis extending from the first end tothe second end. Two feed lip grooves are formed in a surface of the bodyadjacent to the first end. The feed lip grooves extend parallel to oneanother from the first end toward the second end. A cocking surface isbetween the feed lip grooves. The cocking surface has a width of about0.200 inches to about 0.380 inches.

In other embodiments, a bolt carrier assembly is provided which includesa body having a first end opposite a second end. The body has a centralaxis extending therethrough. The body is configured to accommodate adouble stack, single feed magazine. The central axis extends from thefirst end of the body to the second end of the body. A cocking surfaceis formed in the body adjacent to the first end. A width of the cockingsurface corresponds to a cartridge diameter and is less than 0.400inches.

In one or more embodiments, a firearm assembly is provided whichincludes a barrel having a barrel extension. A plurality of bolt lugrecesses is formed in the barrel extension. The firearm assembly alsoincludes a double stack single feed magazine having two feed lips. Abolt channel is formed between the two feed lips. The firearm assemblyalso includes a bolt carrier assembly which includes a body having afirst end and a second end. The body has a central axis extending fromthe first end to the second end. The body has one or more feed lipgrooves formed therein which are configured to accommodate the feed lipsof the magazine therein. A cocking surface is formed in the body betweenthe feed lip grooves. The cocking surface is substantially parallel tothe one or more feed lip grooves. The cocking surface has a width ofabout 0.200 inches to about 0.380 inches. A bolt is disposed in thefirst end of the body.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofits scope, as the disclosure may admit to other equally effectiveembodiments.

FIG. 1A illustrates a rear view of a loaded double stack/double feedconfigured magazine.

FIG. 1B illustrates a rear view of a loaded single stack/single feedconfigured magazine.

FIG. 2 illustrates a top view of a loaded double stack/double feedconfigured magazine.

FIG. 3 illustrates a rear view of an unloaded double stack/double feedconfigured magazine.

FIG. 4 illustrates top, side, and rear views of a double stack/doublefeed magazine, curved with stiffening grooves.

FIG. 5 illustrates top, side, and rear views of a double stack/doublefeed magazine, straight with stiffening grooves.

FIG. 6 illustrates top, side, and rear views of a double stack/doublefeed magazine, curved without stiffening grooves.

FIG. 7 illustrates top, side, and rear views of a double stack/doublefeed magazine, straight without stiffening grooves.

FIG. 8 illustrates a front view of a barrel extension with feed ramps,according to one or more embodiments.

FIG. 9 illustrates a sectioned side view of a barrel extension.

FIG. 10 illustrates a top view of a loaded double stack/single feedconfigured magazine, according to one or more embodiments.

FIG. 11 illustrates a rear view of an unloaded double stack/single feedconfigured magazine, according to one or more embodiments.

FIG. 12A illustrates a rear view of a loaded double stack/single feedconfigured magazine, according to one or more embodiments.

FIG. 12B illustrates potential “failure zone” forces on cartridges andmagazine bodies in a narrow double stack cartridge configuration,according to one or more embodiments.

FIG. 13A illustrates a rear view of a loaded double stack/single feedconfigured magazine, according to one or more embodiments.

FIG. 13B illustrates “failure zone” forces on cartridges and magazinebodies in a wide double stack cartridge configuration, according to oneor more embodiments.

FIG. 14 illustrates top, side, and rear views of a double stack/singlefeed magazine, curved with stiffening grooves, according to one or moreembodiments.

FIG. 15 illustrates top, side, and rear views of a double stack/singlefeed magazine, straight with stiffening grooves, according to one ormore embodiments.

FIG. 16 illustrates top, side, and rear views of a double stack/singlefeed magazine, curved without stiffening grooves, according to one ormore embodiments.

FIG. 17 illustrates top, side, and rear views of a double stack/singlefeed magazine, straight without stiffening grooves, according to one ormore embodiments.

FIG. 18 illustrates a magazine including a narrow double stack sectionand a wide double stack section.

FIG. 19 illustrates cartridge path locations on a sectioned side view ofa barrel extension.

FIG. 20 illustrates a side perspective view of a bolt carrier, accordingto one or more embodiments.

FIG. 21 illustrates a bottom perspective view of the bolt carrier,according to one or more embodiments.

FIG. 22A illustrates a front perspective view of the bolt carrier,according to one or more embodiments.

FIG. 22B illustrates a front perspective view of the bolt carrier and adouble stack/double feed magazine, according to one or more embodiments.

FIG. 22C illustrates a front perspective view of the bolt carrier and adouble stack/single feed magazine, according to one or more embodiments.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of one ormore embodiments may be beneficially incorporated in other embodimentswithout further recitation.

DETAILED DESCRIPTION

Embodiments described herein generally relate to firearm magazines and acorresponding bolt carrier assembly. More specifically, embodimentsdescribed herein relate to a magazine design that allows for theadvantages of a double stack magazine for high capacity while utilizinga single feed style mechanism for positioning and guiding the cartridgesinto the chamber. The firearm magazine includes a magazine body having awidth to accommodate a double stack of cartridges in a zigzag pattern.The magazine includes a spring coupled to a follower within the magazinebody. The firearm magazine body includes two feed lips coupled to themagazine body. The two feed lips are configured to simultaneously hold asingle cartridge in place in a center of the magazine body to allow abolt carrier to push the single cartridge out of the firearm magazineand into a chamber of a firearm. The bolt carrier includes feed lipchannels configured to accommodate the feed lips therein. A cockingsurface is located between the feed lip channels and has a width of lessthan about 0.400 inches.

Embodiments described herein maintain the double stack configuration forthe loaded cartridges but utilize a single feed design instead of thetraditional double feed design. As mentioned previously, the double feeddesign has two feed lips—one on each side of the magazine which holdsthe top cartridge in each stack in place. Therefore each feed lipretains one cartridge (e.g., the top cartridge is retained by one feedlip). The double stack/single feed design has one set of feed lips thatposition one cartridge in the center top of the magazine. Therefore,both feed lips retain a single cartridge in the center position. Thefeed lips of the single feed design are curved to direct the cartridgesinto the single feed position but do not need to be shaped to match thecurvature of the cartridge case. Instead, the feed lips are angledinward from each side of the magazine at an angle that best guides thecartridges, depending on diameter, from each stack into the center ofthe magazine and into the single feed position.

Embodiments described herein may utilize a narrow double stack cartridgeconfiguration or a wide double stack cartridge configuration. In thenarrow double stack cartridge configuration, each cartridge in the fullyor almost fully loaded magazine touches two other cartridges, except forthe top and bottom cartridges, which only contact one other cartridge(see, e.g., FIG. 12A).

In the wide double stack cartridge configuration, each cartridge in thefully or almost fully loaded magazine touches three or four othercartridges, except for the top and bottom cartridges, which may onlytouch one or two other cartridges (see e.g., FIG. 13A).

In another embodiment, a magazine body may comprise a first section witha first width where the cartridges are arranged in a narrow double stackcartridge configuration, and may also comprise a second section with asecond width where the cartridges are arranged in a wide double stackcartridge configuration, as discussed with respect to FIG. 18 below.

FIG. 10 illustrates a top view of a loaded double stack/single feedconfigured magazine, according to one or more embodiments describedherein. Magazine 300 contains a magazine body 302 and feed lips 308. Asshown, cartridge 114 is centered in the magazine 300 when it is at thetop of the magazine 300 and is the next cartridge 114 to be fed into thechamber of the firearm.

The double stack magazine 300 with a single feed design utilizes asimilar internal design to store the cartridges as the doublestack/double feed high capacity magazine described above in FIGS. 1A and2-7. The double stack/single feed magazine 300 has two vertical columnsof cartridges 114 located next to each other arranged in a zigzag typeconfiguration. The single feed magazine design also utilizes a similarcoil type magazine spring on the inside that extends from the top of themagazine to the bottom, and which utilizes a follower on the top of thespring to guide the cartridges 114 as they are loaded into the magazine.

FIG. 11 illustrates a rear view of an unloaded double stack/single feedconfigured magazine 300, according to an embodiment. The inside of themagazine body 302 contains a follower 306 coupled to magazine spring304. The magazine spring 304 extends from a floor plate 312 to the topof the magazine 300, and is compressed when cartridges 114 are loadedinto the magazine 300. Feed lips 308 and bolt channel 310 are alsoillustrated in FIG. 11. In one or more embodiments, a width of the boltchannel 310 between the feed lips 308 is in a range from about 80% toabout 90%, for example about 85%, of the diameter of the cartridges 114in the magazine 300.

FIG. 12A illustrates a rear view of a loaded double stack/single feedconfigured magazine 300 with a narrow double stack, according to anembodiment. Cartridges 114 are loaded within magazine body 302. Themagazine spring 304 is compressed and extends from floor plate 312 tofollower 306, which is in contact with the bottom-most cartridge 114 inmagazine 300. Feed lips 308 are configured to center the top cartridge114 into bolt channel 310 so that the top cartridge 114 can be fed intothe chamber.

In the narrow double stack cartridge configuration, each cartridge inthe fully or almost fully loaded magazine touches two other cartridges,except for the top and bottom cartridges, which only contact one othercartridge. In the narrow double stack cartridge configuration, the widthof the cartridge stack is approximately less than 150% of the diameterof the cartridge case. Thus, the width of the cartridge stack is outsideof the failure zone as described above.

FIG. 13A illustrates a rear view of a loaded double stack/single feedconfigured magazine 350 with a wide double stack, according to anembodiment. Cartridges 114 are loaded within magazine body 352. Asshown, spring 354 is compressed and extends from floor plate 362 tofollower 356, which is in contact with the bottom-most cartridge 114 inmagazine 350. Feed lips 358 are configured to center the top cartridge114 into bolt channel 360 so that the top cartridge can be fed into thechamber.

In the wide double stack cartridge configuration, each cartridge in thefully or almost fully loaded magazine touches three or four othercartridges, except for the top and bottom cartridges, which may onlytouch one or two other cartridges. In the wide double stack cartridgeconfiguration, the width of the cartridge stack is greater than 180% ofthe diameter of the cartridge case. Thus, the width of the cartridgestack is outside of the failure zone as described above.

Although the double stack/single feed magazine designs illustrated inFIGS. 12A and 13A maintain the double stack configuration, the singlecentered feed location allows the width of the double stack ofcartridges to be altered to maximize the stack geometry withoutaffecting the functioning of the magazine. The altered stack geometryallows a fixed size magazine to accept a larger range of cartridgediameters.

The single feed design also requires less force from the bolt as thefirearm cycles because the cartridge is easily fed from the magazine andinto the chamber with less resistance. The double feed design, incontrast, requires more force from the bolt to overcome the resistancecreated when the cartridges engage the feed ramps and are redirectedinto the chamber. As the projectile in the cartridge engages the feedramp as the cartridge moves forward, the rear half of the cartridge caseis still under the feed lip. As the front of the cartridge is deflectedup due to the contact with the feed ramp, the rear of the cartridge isdeflected down and must push the remaining cartridges in the magazinedown and compress the magazine spring until the rear of the cartridge ispushed out from under the feed lip. This movement also causes resistanceon the bolt as the cartridge is fed from the magazine.

The double stack/single feed magazine functions in much the same manneras a traditional double stack/double feed magazine in that thecartridges are removed or “stripped” from the magazine by the bolt asthe firearm cycles. Both designs utilize a magazine spring that pushesthe cartridges up from the bottom of the magazine and “feeds” them asthe firearm cycles, while the cartridges are retained in the magazine bythe feed lips at the top of the magazine.

The double stack/single feed design, however, allows the magazine feedlips to present the cartridge in a centered and more elevated positionwhen compared to a traditional double stack/double feed design. Acomparison of FIGS. 1A and 13A illustrates the difference of theposition of the top cartridge in the magazine between the double feeddesign (FIG. 1A) and the single feed design (FIG. 13A). The elevated andcentered location in the single feed design positions the cartridge morein line with the chamber of the firearm and allows the cartridge to bestripped or fed from the magazine by the bolt and directly into thechamber with less opportunity for the projectile to contact any feedramps or bolt lug recesses or any other parts of the firearm.

Cartridges fed from a magazine with a single feed design are generallymore accurate than those from a traditional double feed design becausethe projectiles are not damaged as the cartridges are fed from themagazine and into the chamber.

FIG. 14 illustrates top, side, and rear views of a double stack/singlefeed magazine 300, curved with stiffening grooves 316, according to anembodiment. As seen in the side view of the magazine 300, the magazine300 is curved and includes a number of stiffening grooves 316. The feedlips 308 are also visible in the top, side, and rear views of themagazine 300. The bolt channel 310 is shown in the rear view of themagazine 300.

FIG. 15 illustrates top, side, and rear views of a double stack/singlefeed magazine 300, straight with stiffening grooves 316, according to anembodiment. As seen in the side view of the magazine 300, the magazine300 is straight from the top to the bottom and includes a number ofstiffening grooves 316. The feed lips 308 are also visible in the sideand rear views of the magazine 300. The bolt channel 310 is shown in therear view of the magazine 300.

FIG. 16 illustrates top, side, and rear views of a double stack/singlefeed magazine 300, curved without stiffening grooves, according to anembodiment. As seen in the side view of the magazine 300, the magazine300 is curved. The feed lips 308 are also visible in the side and rearviews of the magazine 300. The bolt channel 310 is shown in the rearview of the magazine 300.

FIG. 17 illustrates top, side, and rear views of a double stack/singlefeed magazine 300, straight without stiffening grooves, according to anembodiment. As seen in the side view of the magazine 300, the magazine300 is straight from the top to the bottom. The feed lips 308 are alsovisible in the side, top, and rear views of the magazine 300. The boltchannel 310 is shown in the rear and top view of the magazine 300.

FIG. 18 illustrates an example of a double stack/single feed magazine400, according to another embodiment. The magazine 400 comprises feedlips 408 atop a magazine body 402. Floor plate 412, spring 404, andfollower 406 are also illustrated. In this embodiment, the magazine body402 is larger at the bottom of the magazine 400 than at the top.Therefore, the stack geometry of the cartridges 114 in the magazine 400contains cartridges 114 in a wide or standard double stack pattern atthe bottom of the magazine 400 and cartridges 114 in a narrow doublestack pattern at the top of the magazine 400. In one or moreembodiments, the bottom portion of the magazine 400 is approximately 20%wider than the top portion of the magazine 400. In another embodiment,the bottom portion of magazine 400 is greater than 20% wider than thetop portion of the magazine 400.

The structure of the magazine 400 allows the narrower top portion of themagazine 400 to fit into an existing smaller magazine well of a firearm,while the wider bottom portion allows for more cartridges to fit intothe magazine 400.

FIG. 19 illustrates cartridge path locations on a sectioned side view ofa barrel extension 200. A chamber 204 is shown in barrel 210. Feed ramps202 are also illustrated. As described with respect to FIG. 9 above, alower projectile position 220 for a double feed magazine is illustratedwith an arrow. Also illustrated in FIG. 19 with an arrow is an upperprojectile position 230 for a single feed magazine. In a double feedmagazine, the tip of the projectile is located in the lower projectileposition 220. In this lower projectile position 220, the projectile maymiss the leading edge of the feed ramp 202 and stop moving forward whenthe projectile hits the flat inside surface of the barrel extension 200or upper receiver, thereby causing a feed jam and causing the firearm tomalfunction. However, with a single feed magazine according to theembodiments described herein, the tip of the projectile is located inthe upper projectile position 230. In this position, the cartridge willnot hit the flat surface of the barrel extension 200 and stop movingforward. Instead, the cartridge is more likely to clear the barrelextension 200 and be loaded into the chamber 204 of the firearm withoutbeing obstructed or damaged. Therefore the double stack/single feedmagazine as described herein provides an advantage over the conventionaldouble stack/double feed magazine.

To disassemble one or more embodiments of the double stack/single feedmagazine as described herein, the floor plate is removed by sliding thefloor plate to the front or rear and off of the bottom of the magazine.Then, the coil spring and follower are removed by pulling them out thebottom of the magazine. Assembly of the magazine is in reverse order ofdisassembly.

Due to the single feed position in the center of the magazine having abolt channel narrower than the cartridge case, loading of the cartridgesmust occur one at a time with the cartridges pushed into position fromthe front, which depresses the follower and slides the cartridge downand under the feed lips. Additional cartridges are fed the same way bydepressing the cartridge that is already in the magazine down andsliding the next cartridge into the magazine on top of the one alreadyin the magazine. The magazine is unloaded by sliding the cartridges outfrom under the feed lips from back to front one at a time until themagazine is empty.

FIG. 13B illustrates forces 510 in a wide double stack magazine. In thewide double stack magazine, the magazine body 502 contains thecartridges 114. The forces 510 in the wide double stack magazine aregenerally straight up and down, and do not push against the sides of themagazine body.

FIG. 12B illustrates potential forces 512 in a narrow double stackmagazine. The body 504 of the narrow double stack magazine containscartridges 114. Forces 512 push outward against the body 504. The forces512 can wedge the cartridges 114 in place, depending on the magnitude ofthe forces 512 and the angle of the forces 512. The forces 512 can causethe magazine to fail if the magazine is not constructed to accommodatethe proper width of the cartridge stack. As described above, the“failure or wedge zone” where the cartridges 114 exert forces to theoutside walls of the magazine is approximately 150% to 180% of thediameter of the cartridge case. Previous attempts to adapt largercartridges to existing magazines have resulted in failure because thewidth of the stack of cartridges falls in the failure zone.

FIG. 20 illustrates a side perspective view of a bolt carrier 600,according to one or more embodiments. The bolt carrier 600 includes abody 602 with a first end 620 and a second end 622 opposite the firstend 620. A stepped surface 606 is formed in the body 602 adjacent to thefirst end 620. The stepped surface 606 may be used to engage a charginghandle (not shown) to manually cycle the bolt rearward in the firearmassembly. A cocking surface 612 is formed in the body 602 adjacent tothe first end 620 of the body 602. The cocking surface 612 is oppositethe stepped surface 606 of the body 602. In one or more embodiments,each end of the cocking surface 612 is beveled. A feed lip groove isformed on either side of the cocking surface 612. In some embodiments,the feed lip grooves define at least a portion of the cocking surface612. The feed lip grooves are discussed in more detail below.

A recess 608 is formed into a side of the body 602. One or more gasexhaust ports 610 are formed in the recess 608. The one or more gasexhaust ports 610 enable a gas pressure built up inside the body 602 tobe exhausted outside the firearm. An opening 618 formed in the body 602adjacent to the plurality of forward assist notches 614 enables excessgas inside the bolt carrier 600 to be exhausted outside the firearm. Afiring pin retaining hole 616 is also formed in the body 602 adjacent tothe plurality of forward assist notches 614. The firing pin retaininghole 616 enables a firing pin retaining pin (not shown) to be insertedto retain a firing pin (not shown) of the firearm inside the boltcarrier 600.

The body 602 is generally cylindrical in shape, as depicted in FIG. 20.The body 602 is configured to have a bolt (not shown) inserted into thebolt carrier at the first end 620. A plurality of forward assist notches614 is formed in a side of the body 602. The notches 614 are engaged bya forward assist (not shown) in the firearm assembly to force the boltcarrier 600 forward so that the bolt in the bolt carrier 600 engages thebarrel extension lugs 212 illustrated in FIG. 9.

A bolt (not shown) is inserted into the first end 620 of the boltcarrier 600. As the bolt carrier 600 cycles in the firearm, the boltmoves with the bolt carrier 600. The bolt is held in the bolt carrier600 via a cam pin (not shown). The cam pin is retained in the boltcarrier 600 by a firing pin (not shown) which is inserted into thesecond end 622 of the bolt carrier 600. The firing pin is held in thebolt carrier 600 by a firing pin retaining pin (not shown). Theassembled combination of the bolt carrier 600 along with componentswhich are not illustrated, such as the bolt, the cam pin, the firingpin, and the firing pin retaining pin are referred to as a “bolt carriergroup.”

When a cartridge 114 is fired, the bolt carrier 600 moves from a forwardposition to a rearward position to eject an empty cartridge case. As thebolt carrier 600 moves to the rearward position, the cocking surface 612contacts and cocks a hammer (not shown) in the firearm. Once in therearward position, the bolt carrier 600 moves to the forward position,passing over the magazine 300. As the bolt carrier 600 passes over themagazine 300, the top cartridge 114 in the magazine 300 is pushed orstripped from the magazine 300 toward the barrel extension 200.

FIG. 21 illustrates a bottom perspective view of the bolt carrier 600,according to one or more embodiments. The cocking surface 612 isdisposed between feed lip grooves 624. The feed lip grooves 624 areformed in the body 602 and extend from the first end 620 of the bodytoward the second end 622 of the body. In one or more embodiments, thefeed lip grooves 624 are recesses formed into the body 602. The feed lipgrooves 624 are shaped to accommodate a magazine feed lip, such as thefeed lips 308 illustrated in FIG. 10.

A width 629 of the cocking surface 612 is configured to enable the boltcarrier 600 to be used with a double stack/single feed magazine 300designed for various cartridge sizes. A width of the bolt channel 310corresponds to a diameter of the cartridges 114 loaded in the magazine300. That is, as the size of cartridges 114 in the magazine 300increases, the width of the bolt channel 310 between the feed lips 308of the magazine 300 also increases. In one or more embodiments, thewidth of the bolt channel 310 is in a range from about 80% to about 95%of the diameter of the cartridge loaded in the magazine 300, such as arange from about 82% to about 90%, for example, about 85%. For example,the width of the bolt channel 310 is about 0.321 inches for a cartridge114 having a diameter of about 0.378 inches; the width of the boltchannel 310 is about 0.359 inches for a cartridge 114 having a diameterof about 0.422 inches; the width of the bolt channel 310 is about 0.374inches for a cartridge 114 having a diameter of about 0.440 inches; thewidth of the bolt channel 310 is about 0.380 inches for a cartridge 114having a diameter of about 0.447 inches.

As the width of the bolt channel 310 is modified to accommodate variousdiameters of the cartridge 114, the width 629 of the cocking surface 612is also modified to accommodate the various widths of the bolt channel310. For example, a conventional bolt carrier for an AR15/M4 style riflehas a cocking surface with a width of about 0.400 inches. To enable useof the bolt carrier 600 with a double stack/single feed magazine 300,the width 629 of the cocking surface 612 is reduced to less than 0.400inches, such as in a range from about 0.200 inches to 0.380 inches, forexample, about 0.300 inches. That is, the width 629 of the cockingsurface 612 should be less than a width of the bolt channel 310 betweenthe feed lips 308 of the magazine 300.

A recess 626 is formed in a rear section 604 of the bolt carrier 600. Atapered portion 628 of the bolt carrier 600 is formed at an end of thecocking surface 612 opposite the first end 620 of the bolt carrier 600.The tapered portion 628 is configured to contact the hammer of thefirearm when the bolt carrier 600 moves toward the rearward position.The tapered portion 628 enables the hammer to be pushed downward tobegin cocking the hammer. The cocking surface 612 completes cocking thehammer by pushing the hammer downward into a cocked position.

FIG. 22A illustrates a front perspective view of the bolt carrier 600,according to one or more embodiments. As shown, the feed lip grooves 624are formed in the body 602. The feed lip grooves are recesses formedinto a bottom surface of the bolt carrier 600. A protrusion 654 isformed between the feed lip grooves 624. The cocking surface 612 isdisposed on the protrusion 654 at a distance 652 from a central axis 650of the bolt carrier 600. The central axis 650 extends along the boltcarrier substantially parallel to the feed lip grooves 624 and thecocking surface 612. The distance 652 is in a range from about 0.25inches to about 0.5 inches, such as in a range from about 0.35 inches toabout 0.40 inches, for example, about 0.37 inches. In some embodiments,a maximum width of the cocking surface 612 is about 0.39 inches. Inother embodiments, the width of the cocking surface is from about 0.39inches, about 0.38 inches, about 0.37 inches, 0.36 inches, or 0.35inches to about 0.3 inches, 0.25 inches, 0.2 inches, or about 0.1inches. For example, the width of the cocking surface may be from about0.37 to about 0.25, such as, about 0.35 inches.

In some embodiments, the cocking surface 612 is substantially tangentialto the bolt carrier 600. The cocking surface 612 and the protrusion 654may be fabricated with various profiles. In some embodiments, thecocking surface 612 is a surface of the protrusion 654 that is farthestfrom the central axis 650 and opposite the stepped surface 606illustrated in FIG. 20. The cocking surface 612 may be concave, convex,pointed, substantially planar, etc. In some embodiments, the protrusion654 is defined by two, three, four, five, or more surfaces including thecocking surface 612. In some embodiments, the cocking surface 612 mayinclude one or more surfaces between the feed lip grooves 624. A widthof the protrusion 654 may be smaller or larger than a width of thecocking surface 612.

FIG. 22B illustrates a front perspective view of the bolt carrier 600and a double stack/double feed magazine 630, according to one or moreembodiments. The feed lip grooves 624 are configured to enable the feedlips 632 of the magazine 630 to pass therethrough as the bolt carrier600 moves between the forward position and the rearward position. Thecocking surface 612 of the bolt carrier 600 is configured to passbetween the feed lips 632 of the magazine 630 as the bolt carrier 600moves in the firearm.

FIG. 22C illustrates a front perspective view of the bolt carrier 600and a double stack/single feed magazine 640, according to one or moreembodiments. A cocking surface 615 between the feed lip grooves 624 isnarrowed compared to the cocking surface 612 illustrated in FIG. 22B.The cocking surface 615 is narrowed to enable the feed lips 642 of thedouble stack/single feed magazine 640 to pass through the feed lipgrooves 624 as the bolt carrier 600 moves between the forward positionand the rearward position. In some embodiments, the cocking surface 615is narrowed as the feed lip grooves 624 are widened.

The double stack/single feed magazine described herein has a number ofadvantages over conventional magazines. First, the double stack/singlefeed magazine maintains the high capacity design of conventionalmagazines. Second, the double stack/single feed magazine does not damageprojectiles as much as the conventional design. Finally, the doublestack/single feed magazine is easily adaptable for use with largerdiameter cartridges.

The bolt carrier with a narrow cocking surface can be used with variouscartridge sizes that are larger than a cartridge size of standardAR15/M4 rifles. The narrow cocking surface enables the bolt carrier tobe used with a double stack/single feed magazine. The doublestack/single feed magazine enables cartridges to be used that are largerthan those that can be used with a double stack/double feed magazine.The combination of the double stack/single feed magazine and the narrowcocking surface enables the firearm to function properly when firingcartridges larger than the cartridges for which the firearm wasdesigned.

Some embodiments herein discuss semiautomatic and automatic firearms,particularly semiautomatic and automatic rifles that utilize barrelextensions. Embodiments described herein may also be utilized in boltaction rifles that utilize feed ramps with appropriate modifications, ifnecessary. Embodiments herein may utilize any magazine capacity, fromone cartridge to forty cartridges or even higher.

Certain embodiments and features have been described using a set ofnumerical upper limits and a set of numerical lower limits. It should beappreciated that ranges including the combination of any two values,e.g., the combination of any lower value with any upper value, thecombination of any two lower values, and/or the combination of any twoupper values are contemplated unless otherwise indicated.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

What is claimed is:
 1. A bolt carrier assembly, comprising: a bodyhaving an elongated cylindrical shape with a first end opposite a secondend, the body having a central axis extending from the first end to thesecond end; two feed lip grooves formed in a surface of the bodyadjacent to the first end, the feed lip grooves extend parallel to oneanother from the first end toward the second end; and a cocking surfacebetween the feed lip grooves, the cocking surface having a width ofabout 0.200 inches to about 0.380 inches.
 2. The bolt carrier assemblyof claim 1, wherein the cocking surface is parallel to the feed lipgrooves.
 3. The bolt carrier assembly of claim 1, wherein the bodyfurther comprises a stepped surface formed in the body.
 4. The boltcarrier assembly of claim 3, wherein the stepped surface is opposite andparallel to the cocking surface.
 5. The bolt carrier assembly of claim1, wherein a width of the cocking surface is about 28% to about 38% of awidth of the body.
 6. The bolt carrier assembly of claim 1, wherein thebody further comprises a tapered portion adjacent to the cocking surfaceand the cocking surface is between the tapered portion and the first endof the body.
 7. The bolt carrier assembly of claim 6, wherein thecocking surface extends between the first end and the tapered portion.8. A bolt carrier assembly, comprising: a body having a first endopposite a second end, the body having a central axis extendingtherethrough, the central axis extending from the first end to thesecond end; and a cocking surface formed in the body adjacent to thefirst end, a width of the cocking surface corresponding to a cartridgediameter, the width of the cocking surface less than 0.400 inches, thebody configured to accommodate a double stack, single feed magazine. 9.The bolt carrier assembly of claim 8, wherein the width of the cockingsurface is about 28% to about 38% of a width of the body.
 10. The boltcarrier assembly of claim 8, wherein the width of the cocking surface isabout 0.200 inches to about 0.380 inches.
 11. The bolt carrier assemblyof claim 8, further comprising a stepped surface formed in the bodyopposite the feed lip grooves.
 12. The bolt carrier assembly of claim11, wherein the stepped surface is opposite and parallel to the cockingsurface.
 13. The bolt carrier assembly of claim 12, wherein the bodyfurther comprises a tapered portion adjacent to the cocking surface andopposite the first end of the body.
 14. The bolt carrier assembly ofclaim 13, wherein the cocking surface extends between the first end andthe tapered portion.
 15. The bolt carrier assembly of claim 13, whereinthe body further comprises two feed lip grooves formed in the bodyadjacent to the first end, the feed lip grooves are parallel to oneanother opposite the stepped surface, and the feed lip grooves extendfrom the first end to the tapered portion.
 16. A firearm assembly,comprising: a barrel having a barrel extension; a plurality of bolt lugrecesses formed in the barrel extension; a double stack single feedmagazine having two feed lips, wherein a bolt channel is formed betweenthe two feed lips; and a bolt carrier assembly comprising: a body havinga first end and a second end, the body having a central axis extendingfrom the first end to the second end; one or more feed lip groovesformed in the body, the feed lip grooves configured to accommodate thefeed lips therein; a cocking surface formed in the body between the feedlip grooves, the cocking surface substantially parallel to the one ormore feed lip grooves, the cocking surface having a width of about 0.200inches to about 0.380 inches; and a bolt disposed in the first end ofthe body.
 17. The firearm assembly of claim 16, wherein the boltcomprises a plurality of bolt lugs, each bolt lug of the plurality ofbolt lugs corresponding to at least one bolt lug recess of the pluralityof bolt lug recesses which correspond to the plurality of bolt lugrecesses.
 18. The firearm assembly of claim 16, wherein a width of thebolt channel is about 80% to about 90% of a diameter of a cartridge inthe double stack single feed magazine.
 19. The firearm assembly of claim16, wherein the cocking surface of the body is configured to bepositioned between the feed lips of the double stack single feedmagazine.
 20. The firearm assembly of claim 16, wherein the boltcomprises a tapered portion and the cocking surface extends between thefirst end and the tapered portion.